Vocal fold palsy after use of the laryngeal mask airway

The place of ultrasonography in confirming the position of the laryngeal mask airway in pediatric patients: an observational study

Background and objectives

Laryngeal mask airways are increasingly used as supraglottic devices during general anesthesia. Ultrasonography can provide a dynamic image simultaneous to placing the supraglottic airway device. In the current study, the incidence of suboptimal laryngeal mask airway position and replacement in children was evaluated using simultaneous ultrasonographic imaging.

Methods

A prospective observational study was conducted on 82 patients aged 3–15 years with American Society of Anesthesiologists (ASA) physical status I or II. Patients under general anesthesia and with airway provided by a laryngeal mask airway were included. The position of the laryngeal mask airway was evaluated by ultrasonography on two planes. According to our scoring system, Grade I and Grade II were determined to indicate acceptable placement, while Grade III was determined to indicate unacceptable placement. Suboptimal laryngeal mask airway placement rates and the requirement of replacement were determined. Laryngeal mask airway placement optimized by ultrasonography was evaluated with both leak tests and a fiberoptic laryngoscope.

Results

The average age of the patients was 6.27 ± 4.66 years. After evaluation with ultrasonography, 65 (79.3%) of the laryngeal mask airways were found to be optimally positioned, while the position of 13 (15.9%) had to be corrected, and 4 (4.9%) had to be replaced. There was a moderate positive correlation between the ultrasonographic evaluation and leak test evaluation (p < 0.001; r = 0.628). Relocation of the laryngeal mask airway was determined to be an independent risk factor affecting the development of complications (OR = 2.961; p = 0.046; 95% Cl 2.850–30.745).

Conclusion

The use of ultrasonography to verify and relocate laryngeal mask airway placement is noninvasive and effective.

Two Cases of Bilateral Vocal Fold Mobility Impairment After LMA Use In 7 Months

OBJECTIVES

To increase awareness of vocal fold mobility impairment secondary to laryngeal mask airway (LMA) use in the operating room.

METHODS

We report 2 cases of bilateral vocal fold mobility impairment after LMA use within 7 months of each other. One patient is a 52-year-old female who developed this complication after orthopedic elbow surgery. The second case is a 75-year-old male who presented after undergoing inguinal hernia repair.

RESULTS

The patient from the first case required a 7-day hospital stay in the SICU due to airway compromise with spontaneous resolution of right-sided vocal fold immobility and improvement of symptoms. The 75-year-old male required direct laryngoscopy and bilateral true vocal fold injection medialization to correct his bilateral vocal fold paresis causing dysphonia and aspiration of liquids.

CONCLUSIONS

Bilateral vocal fold immobility secondary to LMA use is likely an underreported phenomenon of which otolaryngologists and anesthesiologists should be aware. Presentation may be severe, requiring hospitalization or operative intervention.

Unilateral Vocal Cord Paralysis following Insertion of a Supreme Laryngeal Mask in a Patient withSjögren’sSyndrome

Since its introduction in 1988 by Dr. Archie Brain, the laryngeal mask airway (LMA) is being used with increasing frequency. Its ease of use has made it a very popular device in airway management and compared to endotracheal intubation it is less invasive. The use of LMA was on the rise, so has been the incidence of its related complications. We report severe unilateral vocal cord paralysis following the use of the supreme laryngeal mask (sLMA) in a patient with Sjögren's syndrome. In addition, we propose possible mechanisms of injury, review the existing case reports, and discuss our findings.

Complications Associated with the Use of Supraglottic Airway Devices in Perioperative Medicine

Supraglottic airway devices are routinely used for airway maintenance in elective surgical procedures where aspiration is not a significant risk and also as rescue devices in difficult airway management. Some devices now have features mitigating risk of aspiration, such as drain tubes or compartments to manage regurgitated content. Despite this, the use of these device may be associated with various complications including aspiration. This review highlights the types and incidence of these complications. They include regurgitation and aspiration of gastric contents, compression of vascular structures, trauma, and nerve injury. The incidence of such complications is quite low, but as some carry with them a significant degree of morbidity the need to follow manufacturers' advice is underlined. The incidence of gastric content aspiration associated with the devices is estimated to be as low as 0.02% with perioperative regurgitation being significantly higher but underreported. Other serious, but extremely rare, complications include pharyngeal rupture, pneumomediastinum, mediastinitis, or arytenoid dislocation. Mild short-lasting adverse effects of the devices have significantly higher incidence than serious complications and involve postoperative sore throat, dysphagia, pain on swallowing, or hoarseness. Devices may have deleterious effect on cervical mucosa or vasculature depending on their cuff volume and pressure.

Supraglottic Airway Devices and Effect on Voice-Comparison of LMA Proseal and i-gel: Double-Blind Randomized Clinical Trial

OBJECTIVES

Laryngeal mask airway (LMA) is an important alternative to endotracheal intubation for all professional voice users undergoing surgery. However, dysphonia is a known complication of LMA Proseal (PLMA) use. The i-gel airway (IGA) provides adequate airway seal without the need for an inflatable cuff. Hence, it helps to minimize the risk of tissue compression. This study compares effect of PLMA and IGA on voice at 24th hour after anesthesia.

DESIGN

This is a double-blind randomized clinical trial.

METHODS

Ninety anesthesiologists class 1 adults scheduled for surgeries lasting up to 60-120 minutes were included in the study. Participants were randomly allocated to group PLMA (n = 43) and group IGA (n = 43). Cuff pressure was monitored and maintained at just seal pressure in group PLMA. Voice was evaluated using perceptive and acoustic analysis (jitter, shimmer, and harmonics-to-noise ratio [HNR]) preoperatively and at 24th hour after anesthesia. Voice of patients with pharyngolaryngeal complaints was categorized into rough, breathy, asthenic, strain, or normal pattern.

RESULTS

Acoustic parameters jitter, shimmer, and HNR deteriorated significantly in both group PLMA and IGA albeit the change being comparable. Incidence of pharyngolaryngeal complaints was similar in both the groups. A total of 10% patients in group PLMA and 12.5% in group IGA developed breathy voice significant deterioration in all acoustic variables at 24th postoperative hour, but differences were not significant between group PLMA and group IGA.

CONCLUSIONS

PLMA and IGA both produce comparable and significant deterioration in acoustic variables at 24th hour after short duration general anesthesia.

An ultrasound evaluation of laryngeal mask airway position in pediatric patients: an observational study

BACKGROUND

In children, the laryngeal mask airway (LMA) is frequently displaced within the hypopharynx, resulting in repositioning of the device. When the tip of the LMA is placed in the esophageal inlet, the arytenoids are moved ventrally. When the LMA is rotated or deviated, the ventral movement of the arytenoids may result in asymmetric elevation of an arytenoid cartilage, which can be detected with ultrasound (US). In this study, we sought to estimate the incidence of LMA malposition detected with US in pediatric patients. The primary end point was to compare the incidence of LMA malposition between US and fiber optic bronchoscopy (FOB). The secondary end points were to find the interrelationship between US-detected and FOB-detected malposition of the LMA and to locate the diagnostic performance of US in detecting LMA malposition.

METHODS

In this observational study, 100 consecutive children were included. After anesthetic induction, US evaluation was performed before and after LMA insertion to obtain the glottic image on the anterior neck. FOB was performed to assess LMA position (FOB LMA grade and LMA rotation grade). With a post-LMA US image, the symmetry of the arytenoid cartilages was evaluated. Asymmetrical elevation of an arytenoid cartilage in reference to the glottic midline and the opposite arytenoid cartilage was graded as 0 to 3 (US arytenoid grade). The interrelationships between US arytenoid grade and FOB LMA grade or LMA rotation grade were assessed.

RESULTS

The incidence of asymmetrical elevation of an arytenoid was 50% (95% confidence interval [CI], 40%-60%). On FOB, the incidence of LMA malposition was 78% (95% CI, 69%-86%), and that of LMA rotation was 43% (95% CI, 33%-53%). The incidence of LMA malposition was higher with FOB (P < 0.0001), but the incidence of rotation was similar (P = 0.395). US arytenoid grade did not correlate with FOB LMA grade (P = 0.611) but showed a significant correlation with LMA rotation grade (P < 0.0001; 95% CI, 60%-83%). To detect a rotated LMA, US had a sensitivity of 93% (95% CI, 81%-98%) and a specificity of 82% (95% CI, 70%-91%). The positive and negative predictive values were 80% (95% CI, 66%-90%) and 94% (95% CI, 83%-99%), respectively. The accuracy was 87% (95% CI, 79%-93%).

CONCLUSIONS

Although US could not detect the suboptimal depth of an LMA, US has promise of being an accurate tool in detecting a rotated LMA.

[Tapia's syndrome : Rare complication of securing airways]

Nerve injuries are a rare complication of airway management. Two cases of Tapia's syndrome following orotracheal intubation are reported. Case 1: a 23-year-old male patient underwent an otorhinolaryngology (ENT) surgical procedure with orotracheal intubation. A left-sided Tapia's syndrome was verified 3 days later. Case 2: a 67-year-old patient developed a right-sided Tapia's syndrome following an arthroscopic intervention of the left shoulder in the beach-chair position. In both cases there was permanent damage of both nerves. On the basis of a comprehensive literature survey the reasons for an intubation-induced Tapia's syndrome are discussed. In order to avoid a glottis or immediate subglottic position it is recommended to check and to document the position of the cuff (depth of intubation) and the measured cuff pressure immediately after intubation. It also seems to be advisable to document an overstretched head position if required for the operation.

Postoperative pharyngolaryngeal adverse events with laryngeal mask airway (LMA Supreme) in laparoscopic surgical procedures with cuff pressure limiting 25 cmH₂O: prospective, blind, and randomised study

To reduce the incidence of postoperative pharyngolaryngeal adverse events, laryngeal mask airway (LMA) manufacturers recommend maximum cuff pressures not exceeding 60 cmH₂O. We performed a prospective randomised study, comparing efficacy and adverse events among patients undergoing laparoscopic surgical procedures who were allocated randomly into low (limiting 25 cmH₂O, L group) and high (at 60 cmH₂O, H group) LMA cuff pressure groups with LMA Supreme. Postoperative pharyngolaryngeal adverse events were evaluated at discharge from postanaesthetic care unit (PACU) (postoperative day 1, POD 1) and 24 hours after discharge from PACU (postoperative day 2, POD 2). All patients were well tolerated with LMA without ventilation failure. Before pneumoperitoneum, cuff volume and pressure and oropharyngeal leak pressure (OLP) showed significant differences. Postoperative sore throat at POD 2 (3 versus 12 patients) and postoperative dysphagia at POD 1 and POD 2 (0 versus 4 patients at POD 1; 0 versus 4 patients at POD 2) were significantly lower in L group, compared with H group. In conclusion, LMA with cuff pressure limiting 25 cmH₂O allowed both efficacy of airway management and lower incidence of postoperative adverse events in laparoscopic surgical procedures. This clinical trial is registered with KCT0000334.

The video laryngoscopes, blind spots and retromolar trigonum injury by the GlideRite(®) rigid stylet

We report the first case of retromolar trigonum tissue injury in an 80-year-old female, caused by the Rigid GlideScope® Stylet. This complication was discovered during oral surgery.

Fibreoptic Assessment of Paediatric Sized Laryngeal Mask Airways

Laryngeal mask airways (LMA) are commonly used in paediatric anaesthesia. A well-placed LMA should provide a direct view of the vocal cords facilitating bronchoscopy or fibreoptic intubation. The aim of this audit was to assess the bronchoscopie view of the glottis obtained through an LMA with regard to its size.

We prospectively assessed the position of LMAs in relation to the glottic aperture in 350 children (zero to seven years) undergoing elective fibreoptic examination of the upper and/or lower airways. Following induction of anaesthesia and positioning of the LMA, a fibreoptic evaluation of the view of the glottis was performed (complete, partial or no visualisation).

Chest movement on manual ventilation was judged as good in the majority of patients and adequate for the remainder. No overt signs of airway obstruction were noted in any patient. However, a complete view of the glottic aperture was present in only 50% of size 1 LMAs, 57.5% of size 1.5, 72.7% of size 2 and 77.8% of size 2.5. The epiglottis impinged on the LMA opening, partially obstructing the view of the glottis in 36.3% of size 1 LMAs, 31.5% of size 1.5, 21% of size 2 and 17.8% of size 2.5. In 13.7% of size 1 LMAs, 11% of size 1.5, 6.3% of size 2 and 4.4% of size 2.5, the epiglottis was completely downfolded, obstructing the view of the glottic aperture.

The findings indicate that even if ventilation is judged as adequate, smaller paediatric LMAs are more commonly associated with suboptimal anatomical positioning with partial obstruction of the glottic aperture than larger LMAs, and therefore may require repositioning more often.

[Laryngopharyngeal morbidity following general anaesthesia. Anaesthesiological and laryngological aspects]

Laryngeal and pharyngeal complaints are among the subjective problems most frequently reported by patients after general anaesthesia involving endotracheal intubation, others being pain, nausea and vomiting. Hoarseness, sore throat, and vocal cord injuries restrict patients' social lives, and in some cases also their working lives. The most frequent types of laryngeal injury are swollen mucosa and haematoma of the vocal cords. Vocal cord paralysis occurs much less frequently. Knowledge of the pathophysiological aspects and other relevant factors associated with laryngopharyngeal morbidity are essential cornerstones of quality assurance in perioperative respiratory tract management. In this review specific sections are devoted to the implications of anaesthesia involving endotracheal intubation and laryngeal masks for laryngopharyngeal morbidity, and also particular aspects of thyroid gland surgery, cardiothoracic and bariatric surgery and obstetric and paediatric anaesthesia, and medicolegal aspects.

Age and comorbidity as risk factors for vocal cord paralysis associated with tracheal intubation

BACKGROUND

Vocal cord paralysis after tracheal intubation may be attributed to ageing and comorbidity. However, the relationship between patient characteristics and the risk of vocal cord paralysis is unknown.

METHODS

We prospectively analysed data representing 31 241 consecutive surgery patients who underwent tracheal intubation to determine whether duration of intubation, age, sex, and cardiovascular, cerebrovascular, and metabolic diseases were risk factors for vocal cord paralysis associated with intubation. Patients with vocal cord paralysis from any other causes were excluded.

RESULTS

Twenty-four (0.077%) suffered vocal cord paralysis (left, 16 patients; right, 8 patients). The risk was increased when intubation lasted 3-6 h (odds ratio, 2.0; 95% confidence interval, 1.1-5.6; P = 0.002) or 6 h or more (odds ratio, 14.5; 95% confidence interval, 5.2-40.9; P < 0.0001). The risk was increased in patients aged 50-69 (odds ratio, 3.6; 95% confidence interval, 1.2-11.1; P = 0.02) and 70 yr or above (odds ratio, 3.9; 95% confidence interval, 1.2-12.8; P = 0.02). The risk was increased with diabetes mellitus (odds ratio, 2.5; 95% confidence interval, 1.1-7.3; P = 0.03) and hypertension (odds ratio, 2.1; 95% confidence interval, 1.1-6.0; P = 0.03).

CONCLUSIONS

The risk of vocal cord paralysis was increased three-fold in patients aged 50 or above, two-fold in patients intubated 3-6 h, 15-fold in patients intubated 6 h or more, and two-fold in patients with a history of diabetes mellitus or hypertension. Our results are informative for informed consent, patient counselling, and intubation decision-making.

Bilateral vocal cord paralysis caused by laryngeal mask airway

The laryngeal mask airway (LMA) is regarded as a safer supraglottic airway for general anesthesia compared with conventional endotracheal tubes. We report a case of bilateral vocal cord palsy temporarily observed after using the LMA, which required urgent tracheotomy. Severe swelling of the arytenoid suggested that bilateral recurrent laryngeal nerve palsy was caused by prolonged compression on the pyriform fossa. One month later, vocal cord movements were fully recovered. It should be noted that bilateral vocal cord palsy is a possible complication associated with use of the LMA.

Lingual nerve injury associated with the ProSeal laryngeal mask airway: a case report and review of the literature

We present a case of lingual nerve injury that was associated with use of the ProSeal laryngeal mask airway during shoulder replacement in a 61-yr-old male. We also review other cases of cranial nerve injury, most of which were associated with use of the classic laryngeal mask airway. In principle, the frequency of cranial nerve injuries can be reduced by avoiding insertion trauma, using appropriate sizes, minimizing cuff volume, and early identification and correction of malposition.

Unilateral recurrent laryngeal nerve neuropraxia following placement of a ProSeal laryngeal mask airway in a patient with CREST syndrome

We report a severe unilateral recurrent laryngeal nerve neuropraxia following use of the ProSeal laryngeal mask airway (PLMA) in a 71-year-old female patient with CREST syndrome. She required amputation of the 5th phalanx of foot because of gangrene due to Raynaud's syndrome. Anesthesia was induced with propofol, and a size 3 PLMA was inserted. Anesthesia was maintained with sevoflurane and nitrous oxide for 2 h and the operation was performed uneventfully. On removal of PLMA, the cuff volume was measured to 40 ml. The patient did not complain of respiratory discomfort shortly after PLMA removal. However, the next day she developed dysphagia and hoarseness. Laryngoscopic examination revealed unilateral vocal cord paralysis. Cricothyrotomy was required because of suspected silent aspiration pneumonia. The pharyngolaryngeal complications improved with a mobile vocal cord but slight hoarseness after 2 months. We considered the patient's CREST syndrome with a potential of tissue ischemia, and the high intracuff pressure of the PLMA due to nitrous oxide influx, to be the cause of severe recurrent laryngeal nerve neuropraxia in this case.

Nitrous oxide diffusion into the cuffs of disposable laryngeal mask airways

The aim of this study was to investigate cuff pressure changes found in disposable size 3 laryngeal mask airways (LMAs) from different manufacturers during nitrous oxide exposure and to compare the results with the re-usable Classic LMA. In an in vitro experiment, laryngeal mask airway cuff pressures starting from a baseline pressure of 40 cm H(2)O were recorded using a pressure transducer for 60 min with the laryngeal mask airway cuff exposed to 66% N(2)O in oxygen. Cuff pressure increases within 5 min of nitrous oxide exposure were > 250% in the Classic LMA and were not significantly different from those found in the Marshall laryngeal mask airway. However, they were significantly greater than those in the Soft Seal, the Unique, the AMBU, and Intersurgical laryngeal mask airways, all of which demonstrated stable cuff pressure levels within the first 5 min. The cuff pressure increase following 60 min of nitrous oxide exposure was 13.0 +/- 1.1 and 14.6 +/- 0.7 cm H(2)O in the Intersurgical and Unique laryngeal mask airways, respectively, which was significantly lower than the cuff pressure increase in the Soft Seal and in the Ambu laryngeal mask airways (28.3 +/- 2.9 and 30.9 +/- 1.2 cm H(2)O, respectively). Unlike the re-usable Classic LMA and the disposable Marshall laryngeal mask airway, which have silicone cuffs, the disposable Ambu, Intersurgical, Portex Soft Seal and Unique laryngeal mask airways have cuffs constructed from PVC, which seems to be less susceptible to hyperinflation caused by nitrous oxide diffusion.

[Not all vocal cord failure following thyroid surgery is recurrent paresis due to damage during operation. Statement of the German Interdisciplinary Study Group on Intraoperative Neuromonitoring of Thyroid Surgery concerning recurring paresis due to intubation]

Since the phoniatrician H. Bauer described the first case of recurrent laryngeal nerve palsy most likely caused by intubation some 45 years ago, several case reports have been published. However, systematic analyses regarding the frequency of recurrent laryngeal nerve palsies due to intubation are scarce, and none of them has used the proper methods to demonstrate clearly that such a mechanism exists. Currently available data justify the assumption that not every recurrent laryngeal nerve palsy following thyroid surgery is due to the operation itself and that the damage caused by intubation, however, may only account for a minority of these cases. The differential diagnosis of postoperative recurrent laryngeal nerve palsy requires the use of specific tools which go beyond simple laryngoscopy and include stroboscopy as well as intra- and extralaryngeal electromyography. A partial palsy of recurrent laryngeal nerve due to intubation would be associated with severe dysphonia or aphonia, not with dyspnea because of the typical intermediate position of the paralyzed vocal folds with a normal electromyographic function of the cricothyroid muscle. The use of these methods to identify the nature of postoperative recurrent laryngeal nerve palsy is recommended in cases of regular intraoperative neuromonitoring but postoperatively impaired function of the vocal cords.

[Lesions to lips, oral and nasal cavities, pharynx, larynx, trachea and esophagus due to endotracheal intubation and its alternatives]

Dysphagia of greater than 48 h duration is an indication for indirect laryngoscopy and when odynophagia and otalgia occur simultaneously, the possibility of subluxation of the arytenoids demands an urgent ENT assessment. The potential seriousness of laryngeal lesions following intubation obliges us to use the smallest compatible endotracheal tube. The occurrence of pain cervical surgical emphysema and fever suggests a pharyngeal lesion necessitating the suspension of oral feeding and the initiation of antibiotic therapy with anaerobic activity, while awaiting possible surgical intervention. There is no argument to use a tooth-guard for each intubation, but tooth fragility must be researched. The incidence of nasal fossa trauma is reduced with the use of nasal packs impregnated with local anaesthetic containing a vasoconstrictor. This allows the introduction of a small flexible lubricated tube. Laryngeal mask-induced sore throat is more common than the more serious injuries. The classical technique of introducing a laryngeal mask of appropriate size (4 for women, 5 for men) in which the cuff is inflated to a leak pressure of 20 cm H(2)O reduces this frequency. The facial mask may cause injuries especially with prolonged use. The incidence of pulmonary aspiration, linked to the action of drugs, raised intra-abdominal pressure; an emergent situation or difficult intubation is decreased with the performance of the Sellick maneuver at intubation, rapid induction and the neutralization of gastric acidity. A meticulous technique of insertion of the, individualized anaesthesia, particular vigilance at the time of decurarisation and position changes and a calm awakening assure its optimal use, unless the Proseal laryngeal mask modifies this point of view.

Traumatic complications of airway management

Safe and effective airway management techniques have become a hallmark of modern anesthesiology practice, but even such overwhelmingly successful and life-saving practices come with a cost. This cost is morbidity and mortality secondary to the techniques themselves. Closed claims analysis has shown that adverse outcomes secondary to respiratory events constitute the single largest source of injury to patients (75%). Airway management complications are a significant subset of these outcomes. Difficult intubation was shown to be a factor in only slightly more that one third (38%) of these claims. Six percent of closed claims were for airway trauma. These data indicate that injury frequently occurs without initial difficulty in management of the airway, may occur throughout the perioperative period, and can be unexpected when it occurs. Thorough knowledge of the mechanisms of airway injury associated with different airway management techniques may allow for better patient outcomes. This chapter reviews complications of airway management involving the placement of endotracheal tubes. In addition, because laryngeal mask airways (LMAs) have gained increasing prominence in airway management use in the past 10 years, complications relating to their use will also be reviewed.

Bilateral recurrent laryngeal nerve neuropraxia following laryngeal mask insertion: a rare cause of serious upper airway morbidity

We report the case of a 4-year-old boy who developed bilateral recurrent laryngeal nerve neuropraxia following a routine anaesthetic with a laryngeal mask airway. The possible mechanisms of injury and the ways that this rare but critical complication might be avoided are discussed.

Use of the laryngeal mask airway in otologic surgery

OBJECTIVE/HYPOTHESIS

The combination of intravenous sedation and local infiltration anesthesia is routinely utilized in otologic surgery. Advantages over general anesthesia with endotracheal intubation include ease and speed of induction and emergence, safety, and decreased postoperative discomfort. Anatomic and physiological patient constraints may preclude the use of intravenous sedation and anesthetists inexperienced in this technique may find it difficult to achieve a consistent level of anesthesia appropriate for major otologic surgery. Administration of anesthesia using the laryngeal mask airway (LMA) has been proposed to offer many of the advantages of intravenous sedation with less risk of oversedation and obstructive apnea.

STUDY DESIGN

A retrospective chart review.

METHODS

A review of 100 consecutive adult and pediatric patients undergoing major otologic procedures in which the LMA was utilized.

RESULTS

All laryngeal masks were introduced without a laryngoscope and successful placement was accomplished on the first attempt in 98%. Procedures were performed under spontaneous ventilation and in only one instance was surgery temporarily interrupted because of patient movement. No major complications occurred and no patients required endotracheal intubation. Only three patients complained of mild throat discomfort in the immediate postoperative period.

CONCLUSIONS

The laryngeal mask airway is a safe and effective means of providing anesthesia during major otologic surgery.

Recurrent laryngeal nerve injury caused by a laryngeal mask airway

Although there have been few reports of serious complications with the laryngeal mask airway, we record a case of permanent unilateral vocal cord paralysis following the use of a laryngeal mask airway and review the literature describing injuries, not only to the recurrent laryngeal nerves but also to the hypoglossal and lingual nerves.

The effect of nitrous oxide diffusion on laryngeal mask airway cuff inflation in children

We studied the effect of nitrous oxide (N2O) diffusion on size 2 LMA cuff inflation in 52 children, 38 +/- 21 months of age. LMA cuffs were inflated with air (Group A) or 65% N2O, oxygen and halothane (Group B). Cuffs were inflated in a stepwise manner, achieving a cuff leak pressure of 17 +/- 4 cm H2O for all patients. Cuff volume and intracuff pressure increased in Group A (8.5 +/- 1.0 ml to 10.8 +/- 1.4 ml and 101 +/- 36 mmHg to 152 +/- 42 mmHg, respectively) and decreased in Group B (8.9 +/- 1.0 ml to 6.6 +/- 1.5 ml and 90 +/- 30 mmHg to 53 +/- 37 mmHg, respectively). Cuff leak pressure did not change significantly in either group. We conclude that cuff inflation with a mixture of N2O/oxygen prevents N2O diffusion into the cuff, avoiding cuff overinflation without compromising LMA function.